Nanostructures Based on Conducting Polymers
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Nanotechnology is an emerging field that studies fundamental nanoscale processes and the exploitation of those processes in the development and function of nanodevices. To date, development has been hampered by the need for materials and processes that can perform reproducibly at the nanometer scale. Although at present nanodevice development is dominated by materials made from SiO2 or metals, these materials can suffer from a lack of processability. As an alternative that has met with some success, organic-based materials can be easily processed by a variety of methods including spin coating, evaporation, and printing. Organic and organic/inorganic hybrid materials have been developed for organic light-emitting diodes (OLEDs), field-effect transistors, and other devices. However, organic devices usually suffer from a short lifetime as a consequence of poor mechanical and thermal stability associated with small organic molecules. Although organic/inorganic hybrid materials have better mechanical and thermal stability, there still exists an inherent lack of component compatibility, leading to difficulties in processing, and intercomponent communication.
A promising class of materials for nanodevice application is conducting polymers. Their thermal and environmental stability facilitates use in devices for photochemical and electrochemical applications, and their physical and chemical properties can be easily tailored for specific functions. When conducting polymers were first introduced, their poor solubility in common processing solvents limited their versatility. However, this issue has been addressed through modifying the backbone of the polymer with side chains, such as alkyl and alkoxy groups. With this approach, processing of these materials in either aqueous or organic media has expanded the utility of conducting polymers in OLEDs, electrochromic displays, and coatings for more sensitive materials. Numerous articles are found in the literature reporting devices in the micrometer regime made with conducting polymers.
Although Moore's law predicts a doubling in the number of transistors per chip approximately every 18 months, the limits of traditional patterning techniques are threatening to hinder this advancement. The feature size required to continue this trend is in the < 100 nm regime, where control over feature size is critical and difficult to achieve. New procedures and variations on current methods need to be developed to break this regime barrier. In this article, we will review current approaches to creating conducting polymer nanopatterns, from “template synthesis” to lithography. We discuss the advantages and disadvantages of each method and highlight the unique nanostructures formed with these techniques. These materials are likely to enhance the emerging field of nanoelectronics, while complementing current technology.